Finger biometric sensor including capacitance change sensing pressure sensing circuit and related methods

ABSTRACT

A finger biometric sensor may include a lower conductive layer, an upper conductive layer, and a spacer between the lower and upper conductive layers to define an air gap therebetween. The finger biometric sensor may also include a finger biometric sensing integrated circuit (IC) above the upper conductive layer and capable of deflecting the upper conductive layer toward the lower conductive layer to change a capacitance thereof based upon pressure applied to the finger biometric sensing IC. A pressure sensing circuit may be coupled to the lower and upper conductive layers to sense the change in capacitance.

TECHNICAL FIELD

The present invention relates to the field of electronics, and, moreparticularly, to the field of finger biometric sensors.

BACKGROUND

Fingerprint sensing and matching is a reliable and widely used techniquefor personal identification or verification. In particular, a commonapproach to fingerprint identification involves scanning a samplefingerprint or an image thereof and storing the image and/or uniquecharacteristics of the fingerprint image. The characteristics of asample fingerprint may be compared to information for referencefingerprints already in a database to determine proper identification ofa person, such as for verification purposes.

A fingerprint sensor may be particularly advantageous for verificationand/or authentication in an electronic device, and more particularly, aportable device, for example. Such a fingerprint sensor may be carriedby the housing of a portable electronic device, for example, and may besized to sense a fingerprint from a single-finger.

Where a fingerprint sensor is integrated into an electronic device orhost device, for example, as noted above, it may be desirable to morequickly perform authentication, particularly while performing anothertask or an application on the electronic device. In other words, in someinstances it may be undesirable to have a user perform an authenticationin a separate authentication step, for example switching between tasksto perform the authentication. It may also be desirable for afingerprint sensor to perform other functions beyond authentication.

SUMMARY

A finger biometric sensor may include a lower conductive layer, an upperconductive layer, and a spacer between the lower and upper conductivelayers to define an air gap therebetween. The finger biometric sensormay also include a finger biometric sensing integrated circuit (IC)above the upper conductive layer and capable of deflecting the upperconductive layer toward the lower conductive layer to change acapacitance thereof based upon pressure applied to the finger biometricsensing IC. A pressure sensing circuit may be coupled to the lower andupper conductive layers to sense the change in capacitance. Accordingly,a pressure of the user's finger may be sensed, for example, forexecuting a corresponding device function based upon the sensedpressure.

The finger biometric sensor may further include a first dielectric layerbetween the finger biometric sensing IC and the upper conductive layer.A second dielectric layer may be above the finger biometric sensing IC,for example.

The finger biometric sensor may include a sidewall extending upwardlyfrom the lower conductive layer and defining a recess receiving thereinthe spacer, upper conductive layer and finger biometric sensing IC. Aflexible circuit may be coupled to the finger biometric sensing IC. Thelower conductive layer may have an opening therein receiving theflexible circuit therethrough, for example. The finger biometric sensingIC may include an array of electric field finger biometric sensingpixels, for example.

A method aspect may be directed to a method of sensing a change incapacitance using a finger biometric sensor that includes a lowerconductive layer, an upper conductive layer, a spacer between the lowerand upper conductive layers to define an air gap therebetween, and afinger biometric sensing integrated circuit (IC) above the upperconductive layer. The method may include using a pressure sensingcircuit coupled to the lower and upper conductive layers to sense thechange in capacitance caused by deflection of the upper conductive layertoward the lower conductive layer. The deflection may be based uponpressure applied to the finger biometric sensing IC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an electronic device according to the presentinvention.

FIG. 2 is a schematic block diagram of the electronic device of FIG. 1.

FIG. 3 is a cross-sectional view of the finger biometric sensor of FIG.2.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Referring initially to FIGS. 1-2, an electronic device 20 is nowdescribed. The electronic device 20 illustratively includes a portablehousing 21 and a controller 22 carried by the portable housing. Theelectronic device 20 is illustratively a mobile wireless communicationsdevice, for example, a cellular telephone. The electronic device 20 maybe another type of electronic device, for example, a tablet computer,laptop computer, etc. In some embodiments, the electronic device 20 maybe an integrated circuit for use with another or host electronic device.

Wireless communications circuitry 25 (e.g. a wireless transceiver,cellular, WLAN Bluetooth, etc.) is also carried within the housing 21and coupled to the controller 22. The wireless transceiver 25 cooperateswith the controller 22 to perform at least one wireless communicationsfunction, for example, for voice and/or data. In some embodiments, theelectronic device 20 may not include a wireless transceiver 25.

A display 23 is also carried by the portable housing 21 and is coupledto the controller 22. The display 23 may be a liquid crystal display(LCD), for example, or may be another type of display, as will beappreciated by those skilled in the art. A device memory 26 is alsocoupled to the controller 22.

A finger-operated user input device, illustratively in the form of apushbutton switch 24, is also carried by the portable housing 21 and iscoupled to the controller 22. The pushbutton switch 24 cooperates withthe controller 22 to perform a device function in response to thepushbutton switch. For example, a device function may include a poweringon or off of the electronic device 20, initiating communication via thewireless communications circuitry 25, and/or performing a menu function.

More particularly, with respect to a menu function, the controller 22may change the display 23 to show a menu of available applications basedupon pressing of the pushbutton switch 24. In other words, thepushbutton switch 24 may be a home switch or button, or key. Of course,other device functions may be performed based upon the pushbutton switch24. In some embodiments, the finger-operated user input device 24 may bea different type of finger-operated user input device, for example,forming part of a touch screen display. Other or additionalfinger-operated user input devices may be carried by the portablehousing 21.

Referring now additionally to FIG. 3, the electronic device 20 includesa finger biometric sensor 50 carried by the pushbutton switch 24. Thefinger biometric sensor 50 includes a lower conductive layer 51. Thelower conductive layer 51 may be coupled to a voltage reference, forexample, ground 52. A sidewall 53 extends upwardly from the lowerconductive layer 51 and defines a recess 54 for receiving the componentsof the finger biometric sensor, as will be explained in further detailbelow. The sidewall 53 together with the lower conductive layer 51,define a finger sensor housing or trim, as will be appreciated by thoseskilled in the art.

The finger biometric sensor 50 also includes an upper conductive layer55. The upper conductive layer 55 is spaced apart from the lowerconductive layer 51 by way of a spacer 56 between the upper and lowerconductive layers. The spacer 56 defines an air gap 57 between the upperand lower conductive layers 55, 51.

A first dielectric layer 61 carries the upper conductive layer 55 on alower surface thereof. The first dielectric layer 61 may include glass,for example, and have a thickness that is selected based upon astiffness thereof. In other words, a thicker first dielectric layer 61may increase stiffness, while a thinner first dielectric layer mayreduce stiffness. The first dielectric layer 61 may include anothermaterial. In an example embodiment, the first dielectric layer 61 mayhave a thickness of 210 microns, for example.

The finger biometric sensor 50 also includes a finger biometric sensingintegrated circuit (IC) 62 above the upper conductive layer 55, and moreparticularly, carried by an upper surface of the first dielectric layer61. In an example embodiment, the finger biometric sensing IC 62 mayhave a thickness of about 100 microns, for example.

The finger biometric sensing IC 62 includes an array of electric fieldfinger biometric sensing pixels to sense a user's finger 40 or an objectplaced adjacent the array of finger biometric sensing pixels. The fingerbiometric sensing IC 62 is carried by the pushbutton switch 24 so thatwhen a user or object contacts and/or presses downward on the pushbuttonswitch, data from the user's finger 40 is acquired, for example, forfinger matching and/or spoof detection, as will be described in furtherdetail below. In other words, the finger biometric sensing IC 62 maycooperate with circuitry, as will be explained in further detail below,to be responsive to static contact or placement of the user's finger 40or object. Of course, in other embodiments, for example, where thefinger biometric sensing IC 62 is not carried by a pushbutton switch 24,the array of finger biometric sensing pixels may cooperate withcircuitry to be responsive to sliding contact (i.e. a slide sensor), orresponsive to static placement (i.e. a standalone static placementsensor). Further details of electric field finger biometric sensingpixels are disclosed in U.S. Pat. No. 5,940,526 to Setlak et al.,assigned to the present assignee, and the entire contents of which areherein incorporated by reference.

A second dielectric layer 64 is carried by an upper surface of thefinger biometric sensing IC 62. The second dielectric layer 64 may bedirect bonded to the finger biometric sensing IC 62 which may permit thesecond dielectric layer to be thinner than would otherwise be possibleusing conventional bonding techniques, for example, such as using glue.The second dielectric layer 64 may include sapphire, for example, andmay be oxy-nitride treated. The second dielectric layer 64 may includeanother material. In an example embodiment, the second dielectric layer64 may have a thickness of about 190 microns. In some embodiments, acosmetic coating may be between the upper surface of the fingerbiometric sensing IC 62 and a lower surface of second dielectric layer64.

The first dielectric layer 61 and the lower conductive layer 51 eachhave an opening 65, 66 therein. A flexible circuit 67 is coupled to thefinger biometric sensing IC 62 and extends through the openings 65, 66,and, for example, to the controller 22.

During operation, a user's finger 40 is positioned adjacent the fingerbiometric sensing IC 62, and more particularly, on the second dielectriclayer 64. The user's finger 40 during operation, provides downwardpressure on the second dielectric layer 64, for example, at varyingdegrees, and consequently, downward pressure on the finger biometricsensing IC 62 and first dielectric layer 61. The bottom of the firstdielectric layer 61 moves slightly downward with respect to the lowerconductive layer 51. The finger biometric sensing IC 62 deflects theupper conductive layer 55 toward the lower conductive layer 51 to changea capacitance thereof based upon the pressure applied to the fingerbiometric sensing IC by the second dielectric layer 64. In other words,the upper and lower conductive layers 51, 55 define electrodes of acapacitor that have a varying distance therebetween based upon pressureof the user's finger adjacent the finger biometric sensing IC 62. Thesecond dielectric layer 64 may flex slightly under pressure, forexample, between about 5-10 microns at the center, which may not causefatigue damage particularly if the second dielectric layer isoxy-nitride treated. The lower conductive layer 51 acts as a mechanicalstop in the case of relatively high pressure. The relatively large areadefined by the air gap 57 may increase sensitivity.

The finger biometric sensor 50 also includes a pressure sensing circuit68 coupled to the controller 22 and lower and upper conductive layers51, 55 to sense the change in capacitance. The controller 22 performs atleast one device function based upon the sensed change in capacitance.For example, the controller 22 may cooperate with the pressure sensingcircuit 68 to display on the display 23 a notification screen based upona relatively small pressure, display a home page based upon a largerpressure, and turn on wireless communications functions based upon arelatively large pressure. Of course, the controller 22 may cooperatewith the pressure sensing circuit 68 to perform any number and/or typeof functions based upon different pressures, as will be appreciated bythose skilled in the art.

The controller 22 may also cooperate with the finger biometric sensingIC 62 to determine a finger match based upon finger biometric data. Moreparticularly, the processor 22 may determine a finger match based uponenrollment data stored in the device memory 26. The processor 22 mayalso determine a live finger based upon spoof data. More particularly,the processor 22 may determine a live finger based upon a compleximpedance and/or bulk impedance measurement.

With respect to enrollment, in some embodiments, the controller 22 mayalso cooperate with the pressure sensing circuit 68 to prompt a user,via the display 23, to enroll finger biometric data at varying pressuresof the user's finger adjacent the finger biometric sensing IC 62. Thecontroller 22 may then perform at least one authentication functionbased upon the enrolled finger biometric data at the varying pressures.This may be particularly advantageous, for example, for performing afinger match or authentication with fingers having varying degrees ofirregularities for example, sweat content and temperature variations, aswill be appreciated by those skilled in the art. Additionally, theconfiguration described herein may be advantageous for low-power fingerpressure sensing and increased mechanical robustness, which may, inturn, lead to a smaller finger biometric sensor 50, for example, areduction of between 1-1.4 mm in diameter while maintaining performance.

In some embodiments, the controller 22 may cooperate with the array ofelectric field finger biometric sensing pixels 31 to perform anavigation function, for example. Of course the controller 22 maycooperate with the array of electric field finger biometric sensingpixels 31 and/or other circuitry to perform other or additionalfunctions, as will be appreciated by those skilled in the art.

A method aspect may be directed to a method of sensing a change incapacitance using a finger biometric sensor 50 that includes a lowerconductive layer 51, an upper conductive layer 55, a spacer 56 betweenthe lower and upper conductive layers to define an air gap 57therebetween, and a finger biometric sensing integrated circuit (IC) 62above the upper conductive layer. The method may include using apressure sensing circuit 68 coupled to the lower and upper conductivelayers 51, 55 to sense the change in capacitance caused by deflection ofthe upper conductive layer toward the lower conductive layer. Thedeflection may be based upon pressure applied to the finger biometricsensing IC 62.

The present disclosure recognizes that personal information data,including biometric data, in the present technology, can be used to thebenefit of users. For example, the use of biometric authentication datacan be used for convenient access to device features without the use ofpasswords. In other examples, user biometric data is collected forproviding users with feedback about their health or fitness levels.Further, other uses for personal information data, including biometricdata, that benefit the user are also contemplated by the presentdisclosure.

The present disclosure further contemplates that the entitiesresponsible for the collection, analysis, disclosure, transfer, storage,or other use of such personal information data will comply withwell-established privacy policies and/or privacy practices. Inparticular, such entities should implement and consistently use privacypolicies and practices that are generally recognized as meeting orexceeding industry or governmental requirements for maintaining personalinformation data private and secure, including the use of dataencryption and security methods that meets or exceeds industry orgovernment standards. For example, personal information from usersshould be collected for legitimate and reasonable uses of the entity andnot shared or sold outside of those legitimate uses. Further, suchcollection should occur only after receiving the informed consent of theusers. Additionally, such entities would take any needed steps forsafeguarding and securing access to such personal information data andensuring that others with access to the personal information data adhereto their privacy policies and procedures. Further, such entities cansubject themselves to evaluation by third parties to certify theiradherence to widely accepted privacy policies and practices.

Despite the foregoing, the present disclosure also contemplatesembodiments in which users selectively block the use of, or access to,personal information data, including biometric data. That is, thepresent disclosure contemplates that hardware and/or software elementscan be provided to prevent or block access to such personal informationdata. For example, in the case of biometric authentication methods, thepresent technology can be configured to allow users to optionally bypassbiometric authentication steps by providing secure information such aspasswords, personal identification numbers (PINS), touch gestures, orother authentication methods, alone or in combination, known to those ofskill in the art. In another example, users can select to remove,disable, or restrict access to certain health-related applicationscollecting users' personal health or fitness data.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that the invention is not to be limited to the specificembodiments disclosed, and that modifications and embodiments areintended to be included within the scope of the appended claims.

That which is claimed is:
 1. A finger biometric sensor comprising: alower conductive layer; an upper conductive layer; a spacer between thelower and upper conductive layers to define an air gap therebetween; afinger biometric sensing integrated circuit (IC) above the upperconductive layer and capable of deflecting the upper conductive layertoward the lower conductive layer to change a capacitance thereof basedupon pressure applied to the finger biometric sensing IC; and a pressuresensing circuit coupled to the lower and upper conductive layers tosense the change in capacitance.
 2. The finger biometric sensor of claim1 further comprising a first dielectric layer between the fingerbiometric sensing IC and the upper conductive layer.
 3. The fingerbiometric sensor of claim 1 further comprising a second dielectric layerabove the finger biometric sensing IC.
 4. The finger biometric sensor ofclaim 1 further comprising a sidewall extending upwardly from the lowerconductive layer and defining a recess receiving therein the spacer,upper conductive layer, and finger biometric sensing IC.
 5. The fingerbiometric sensor of claim 1 further comprising a flexible circuitcoupled to the finger biometric sensing IC; and wherein the lowerconductive layer has an opening therein receiving the flexible circuittherethrough.
 6. The finger biometric sensor of claim 1 wherein thefinger biometric sensing IC comprises an array of electric field fingerbiometric sensing pixels.
 7. An electronic device comprising: a housing;wireless communications circuitry carried by the housing; a fingerbiometric sensor carried by the housing and comprising a lowerconductive layer, an upper conductive layer, a spacer between the lowerand upper conductive layers to define an air gap therebetween, a fingerbiometric sensing integrated circuit (IC) above the upper conductivelayer and capable of deflecting the upper conductive layer toward thelower conductive layer to change a capacitance thereof based uponpressure applied to the finger biometric sensing IC, and a pressuresensing circuit coupled to the lower and upper conductive layers tosense the change in capacitance; and a controller coupled to thewireless communications circuitry and the finger biometric sensor andcapable of performing at least one wireless communications function viathe wireless communications circuitry.
 8. The electronic device of claim7 wherein the controller is capable of performing at least one devicefunction based upon the sensed change in capacitance.
 9. The electronicdevice of claim 7 further comprising a display coupled to thecontroller; and wherein the controller cooperates with the pressuresensing circuit to prompt a user, via the display, to enroll fingerbiometric data at varying pressures of the user's finger adjacent thefinger biometric sensing IC.
 10. The electronic device of claim 9wherein the controller is capable of performing at least oneauthentication function based upon the enrolled finger biometric data atvarying pressures.
 11. The electronic device of claim 7 wherein thefinger biometric sensor further comprises a first dielectric layerbetween the finger biometric sensing IC and the upper conductive layer.12. The electronic device of claim 7 wherein the finger biometric sensorfurther comprises a second dielectric layer above the finger biometricsensing IC.
 13. The electronic device of claim 7 wherein the fingerbiometric sensor further comprises a sidewall extending upwardly fromthe lower conductive layer and defining a recess receiving therein thespacer, upper conductive layer, and finger biometric sensing IC.
 14. Theelectronic device of claim 7 further comprising a flexible circuitcoupled to the finger biometric sensing IC; and wherein the lowerconductive layer has an opening therein receiving the flexible circuittherethrough.
 15. The electronic device of claim 7 wherein the fingerbiometric sensing IC comprises an array of electric field fingerbiometric sensing pixels.
 16. The electronic device of claim 7 furthercomprising a pushbutton switch beneath the finger biometric sensor. 17.A method of sensing a change in capacitance using a finger biometricsensor comprising a lower conductive layer, an upper conductive layer, aspacer between the lower and upper conductive layers to define an airgap therebetween, and a finger biometric sensing integrated circuit (IC)above the upper conductive layer, the method comprising: using apressure sensing circuit coupled to the lower and upper conductivelayers to sense the change in capacitance caused by deflection of theupper conductive layer toward the lower conductive layer based uponpressure applied to the finger biometric sensing IC.
 18. The method ofclaim 17 further comprising using a controller coupled to the pressuresensing circuit to perform at least one device function based upon thesensed change in capacitance.
 19. The method of claim 17 furthercomprising using a controller cooperating with the pressure sensingcircuit to prompt a user, via a display coupled to the controller, toenroll finger biometric data at varying pressures of the user's fingeradjacent the finger biometric sensing IC.
 20. The method of claim 19further comprising using the controller to perform at least oneauthentication function based upon the enrolled finger biometric data atvarying pressures.